1. Field of the Invention
The present invention relates to a capping unit that seals (known as “capping”) nozzle apertures in a liquid droplet ejection head and prevents drying of a liquid droplet solvent as well as clogging of the nozzle apertures, and to a method of controlling the capping unit, a liquid droplet ejection apparatus that includes the capping unit, and a device manufacturing method that uses the apparatus.
Priority is claimed on Japanese Patent Application No. 2003-428492, filed Dec. 25, 2003, the contents of which are incorporated herein by reference.
2. Description of Related Art
A liquid droplet ejection head is formed by a pressure generation chamber that houses a liquid droplet solvent, a piezoelectric element that pressurizes the pressure generation chamber, and nozzle apertures that are connected to the pressure generation chamber. As a result of the liquid droplet solvent in the pressure generation chamber being pressurized by the piezoelectric element, a minute quantity of liquid droplet solvent is ejected in the form of liquid droplets from nozzle apertures. In a liquid droplet ejection head having a structure such as this, if liquid droplet solvent evaporates in the vicinity of the nozzle apertures, or if an air bubble becomes blocked inside the liquid droplet ejection head, then a liquid droplet ejection malfunction occurs. Because of this, this type of liquid droplet ejection head requires a capping unit that seals the nozzle apertures so as to prevent drying of a liquid droplet solvent and also prevent blockages in the nozzle apertures.
Even if the nozzle apertures of a liquid droplet ejection head are sealed using a capping unit, if they are sealed for an extended period of time, then as a result of the moisture retaining properties of the liquid droplet solvent deteriorating due to evaporation of the liquid droplet solvent located on the flow path of the liquid droplet solvent and in the nozzle apertures or due to the liquid droplet solvent drying inside the capping unit, an increase in the viscosity of the liquid droplet solvent is generated and the nozzle apertures may become blocked. Because of this, the capping unit provided for the liquid droplet ejection head is one that expels liquid droplet solvent that has thickened in the vicinity of the nozzle apertures or ejects an air bubble that has become blocked in the pressure generation chamber by not only simply sealing the nozzle apertures of the liquid droplet ejection head, but by forcibly causing liquid droplet solvent to be expelled from the nozzle apertures by causing negative pressure to act on the nozzle apertures using a suction pump.
Note that, in addition to methods that use a capping unit, methods of clearing blockages in nozzle apertures include a method that uses a cleaning device that wipes a surface in which the nozzle apertures of the liquid droplet ejection head are formed using a wiper, and a flushing method that forcibly ejects a larger number of liquid droplets than a normal liquid droplet ejection quantity by increasing the pressure that is applied to the pressure generation chamber by the piezoelectric element. A conventional capping unit is described in detail, for example, in Japanese Unexamined Patent Application, First Publication No. H10-264402.
When a blockage forms in a liquid droplet ejection head, the aforementioned suctioning by a capping unit, cleaning by a cleaning device, or flushing is performed. However, if the blockage is not cleared, the suctioning, cleaning or flushing are performed a large number of times. Therefore, the problem has arisen that the ejection quantity of liquid droplet solvent from nozzle apertures where a blockage has not formed increases so that liquid droplet solvent is consumed needlessly.
Moreover, if the suctioning or the like is performed on a plurality of occasions, the problem arises that it takes time for a normal state (i.e., a state in which liquid droplets can be ejected from all the nozzle apertures) to be restored. In recent years, liquid droplet ejection heads have been used for the manufacture of filters used in liquid crystal display apparatuses, micro displays, as well as a variety of devices that have micro patterns. If it takes time until a normal state is restored, then a problem may arise in that throughput (i.e., the number of devices that can be manufactured in a unit time) is reduced by a corresponding amount.
The present invention was conceived in view of the above described circumstances, and it is an object thereof to provide a capping unit that enables blockages and the like in nozzle apertures of a liquid droplet ejection head to be cleared in a short time while restraining the needless consumption of liquid droplet solvent, as well as to a control method for the capping unit, a liquid droplet ejection apparatus that includes the capping unit, and a device manufacturing method that manufactures a device using the liquid droplet ejection apparatus.